Interrelationships between Skin Structure, Function, and Microbiome of Pregnant Females and Their Newborns: Study Protocol for a Prospective Cohort Study

Table 2

Variables.

Variables	Statistics/level of scales	Possible range of measurements	Time of measurement; Women	Time of measurement; Newborn/infant	Source of information
Age	Metric variable	In years, women; In days/months, newborn/infant; 18–45 years, women; 0–28 d, newborn; 1–6 months, infant	Baseline, t0	Delivery + 28 d, t1; Delivery + 6 months, t2	ID card, woman; “U-heft,” newborn/infant; U3: 4^th–5^th week; U5: 6^th–7^th month
Weight	Metric variable	In kg, woman; In kg, newborn/infant	Baseline, t0; Delivery + 28 d, t1; Delivery + 6 months, t2	Delivery + 28 d, t1; Delivery + 6 months, t2	Measurement; “U-heft,” newborn/infant; U3: 4^th–5^th week; U5: 6^th–7^th month
Height	Metric variable	In cm, woman; In cm, newborn/infant	Baseline, t0	Delivery + 28 d, t1; Delivery + 6 months, t2	Self-reporting, woman; “U-heft,” newborn/infant; U3: 4^th–5^thweek; U5: 6^th–7^thmonth
Sex	Nominal variable	Female; Male		Delivery + 28 d, t1	“U-heft,” newborn/infant
					U1 delivery
Habitation	Nominal variable	Urban; Rural	Baseline, t0; Delivery + 28 d, t1; Delivery + 6 months, t2	Delivery + 28 d, t1; Delivery + 6 months, t2	Self-reporting, woman
Newborn/infant’s environment	Nominal variable	Apartment; House		Delivery + 28 d, t1; Delivery + 6 months, t2	Self-reporting, woman
Course of delivery	Nominal variable	Vaginal birth; Caesarean	Delivery + 28 d, t1		“U-heft,” newborn/infant; U1 delivery
Vaginal seeding	Nominal variable	Yes; No		Delivery + 28 d, t1	Self-reporting, woman
Newborn/infant nutrition	Nominal variable	Breastfeeding; Cow-milk-based infant formula (including hypoallergenic (HA) based formula) feeding or combination		Delivery + 28 d, t1; Delivery + 6 months, t2	Self-reporting, woman
Period of newborn/infant nutrition (supplementary feeding)	Metric variable	From week x to week x		Delivery + 28 d, t1; Delivery + 6 months, t2	Self-reporting, woman
Gestational age at birth	Metric variable	In weeks		Delivery + 28 d, t1	“U-heft,” newborn/infant; U1 delivery
Dermatological skin assessment, mother	Nominal variable	Coded by ICD11	Baseline, t0; Delivery + 28 d, t1; Delivery + 6 months, t2		Study MD
Dermatological skin assessment, newborn/infant	(i) Eczema; (ii) Dry skin; (iii) Itchy skin; (iv) Rash; (v) Flexural dermatitis and/or visible dermatitis; (vi) Diaper dermatitis; (vii) Hand, mouth, and foot disease	EASI score: (i) Erythema; (ii) Edema/papulation; (iii) Excoriation; (iv) Lichenification; EASI score: (i) Severity of signs; (1) 0–3; (2) None severe; Dry skin: (ii) Desquamation fissures/rhagades; (iii) Erythema; (iv) Pruritus; Itchy skin: (i) If yes: continuous/intermittent; Rash: yes/no; Diaper dermatitis: yes/no; Hand, mouth, and foot disease: yes/no		Delivery + 28 d, t1; Delivery + 6 months, t2	Study MD
Skin care, mother	Open-ended question		Baseline, t0; Delivery + 28 d, t1; Delivery + 6 months, t2		Self-reporting, woman
Skin care, newborn/infant	Open-ended question			Delivery + 28 d, t1; Delivery + 6 months, t2	Self-reporting, woman
Care givers at home	Nominal variable	(i) Father; (ii) Sibling; (iii) Grandparents; (iv) Au pair; (v) Nursery nurse; (vi) Other		Delivery + 28 d, t1; Delivery + 6 months, t2	Self-reporting, woman
Furred pets at home	Nominal variable	(i) Cat; (ii) Dog; (iii) Others	Baseline, t0; Delivery + 28 d, t1; Delivery + 6 months, t2		Self-reporting, woman
The atopic predisposition of the mother (at least one parent or sibling with physician-diagnosed AD, asthma, or allergic rhinitis/rhinoconjunctivitis as reported by at least one parent but in otherwise good overall health)	Nominal variable	Yes/no	Baseline, t0		Self-reporting, woman
Antibiotic intake	Nominal variable	Yes/no	Baseline, t0; Delivery + 28 d, t1; Delivery + 6 months, t2		Self-reporting, woman
Alcohol consumption	Nominal variable	Yes/no	Baseline, t0; Delivery + 28 d, t1; Delivery + 6 months, t2		Self-reporting, woman
Skin surface topography roughness: (i) RA (arithmetic mean roughness) in μm; (ii) RZ (arithmetic mean roughness from five sampling length) in μm	Metric scaled variable; Mean (SD); Median (IQR)	RA: 0.0–100.0 μm; RZ: 0.0–100.0 μm	Baseline, t0; Delivery + 28 d, t1; Delivery + 6 months, t2	Delivery + 28 d, t1; Delivery + 6 months, t2	Standardized images via visioscan VC 98 USB; (i) RA (arithmetic mean roughness) in μm; (ii) RZ (arithmetic mean roughness from five sampling length) in μm; Skin area: inner forearm
Epidermal thickness in μm	Metric scaled variable; Mean (SD); Median (IQR)	0.0–100.0 μm; (40–60 μm)	Baseline, t0; Delivery + 28 d, t1; Delivery + 6 months, t2	Delivery + 28 d, t1; Delivery + 6 months, t2	Standardized images via optical coherence tomography (OCT); Thorlabs’ Telesto; Epidermal thickness in mm; Skin area: inner forearm
Skin stiffness and elasticity total extensibility (Uf, mm)	Metric scaled variable; Mean (SD); Median (IQR)	0.00–0.50; Uf in mm/degree	Baseline, t0; Delivery + 28 d, t1; Delivery + 6 months, t2	Delivery + 28 d, t1; Delivery + 6 months, t2	Cutometer MPA 580 total extensibility (Uf, mm), structural elasticity (Ur/Uf); Skin area: inner forearm
Transepidermal water loss (TEWL); Transepidermal water loss through the stratum corneum in per hour per m^2	Metric scaled variable; Mean (SD); Median (IQR)	0.0–60.0 g/m^2/h	Baseline, t0; Delivery + 28 d, t1; Delivery + 6 months, t2	Delivery + 28 d, t1; Delivery + 6 months, t2	Tewameter 300; Transepidermal water loss through the stratum corneum in per hour per m^2; Skin area: inner forearm
Skin surface pH	Metric scaled variable; Mean (SD); Median (IQR)	>4 or <7.5	Baseline, t0; Delivery + 28 d, t1; Delivery + 6 months, t2	Delivery + 28 d, t1; Delivery + 6 months, t2	Skin pH-meter® PH 905; Concentration of hydrogen ions; Skin area: inner forearm
Stratum corneum hydration (SCH)	Metric scaled variable; Mean (SD); Median (IQR)	0–120, arbitrary units, whereas higher readings indicate higher stratum corneum hydration	Baseline, t0; Delivery + 28 d, t1; Delivery + 6 months, t2	Delivery + 28 d, t1; Delivery + 6 months, t2	Corneometer CM 825; Capacitance measurement of hydration; Arbitrary CM units 0–120; Skin area: inner forearm
Skin microbiome; Bacterial diversity; Relative abundance of phylotypes (operational taxonomic units, OTUs); Top 5 genera	Metric scaled variable; Alpha diversity; Shannon index	N number of taxonomic groups, for example,; (i) Proteobacteria and Bacteroidetes; (ii) Firmicutes; (iii) Actinobacteria; N amount of bacteria (bacterial load)	Baseline, t0; Delivery + 28 d, t1; Delivery + 6 months, t2	Delivery + 28 d, t1; Delivery + 6 months, t2	Skin microbiome; Alpha diversity; Shannon index; Skin area: inner forearm
Hair measurement	Metric variable	Hair thickness; Hair density; Vellus-terminal-hair ratio	Baseline, t0; Delivery + 28 d, t1; Delivery + 6 months, t2	Delivery + 28 d, t1; Delivery + 6 months, t2	Canfield; Hair Metrix average hair width in μm; Hair count per cm^2; Central scalp area, occipital hair area (woman); central hair area (newborn)
Hair colour	Ordinal variable	Hair colour scale, 1–10	Baseline, t0; Delivery + 28 d, t1; Delivery + 6 months, t2	Delivery + 28 d, t1; Delivery + 6 months, t2	Comparison with hair colour scale